.trac branches were different when generated in different timezones.

Something was magically applying the local timezone even though we
tried to copy the timestamp object directly from the child commit.
Force it to UTC instead to avoid the problem.

Author: apenwarr

subtrac.go

@@ -12,6 +12,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"time"
 )
 
 // A Trac represents a commit or tree somewhere in the project's hierarchy,
@@ -316,7 +317,12 @@ func (c *Cache) newTracCommit(commit *object.Commit, tracs []*object.Commit, hea
 	sig := object.Signature{
 		Name:  "git-subtrac",
 		Email: "git-subtrac@",
-		When:  commit.Committer.When,
+		// This *should* preserve the timezone from the original
+		// commit, but a bug in either go-git or go's time library
+		// prevents that from working and uses the local timezone
+		// instead. We want the generated commits to be identical
+		// no matter who generates them, so let's force UTC instead.
+		When:  commit.Committer.When.In(time.UTC),
 	}
 	emptyTree := object.Tree{}
 	nec := c.repo.Storer.NewEncodedObject()